The present invention relates to a an apparatus for cooling, wherein goods are transferred with the goods arranged along the transferring route and low temperature gas is flowed in a direction reverse to the direction of transferring goods, and thereby the goods are cooled by contacting them with the low temperature gas. In the present invention, freezing is also denominated cooling.
Such a method of and an apparatus for cooling are utilized widely for the purposes such as for preserving food stuffs, hardening plastic substances such as rubber, plastics and the like to pulverize and cooling metal in heat treatment process.
A method and an apparatus of the type mentioned above, which have been proposed or adopted heretofore are described briefly in the sentences which follow. Namely, low temperature gas was flowed substantially in parallel and in a direction reverse to the direction of transferring goods or low temperature gas was flowed across the goods transferring route several times while the crossing position was moved slowly in a direction reverse to the direction of transferring goods. That of such former type, however, could not satisfy simultaneously two requirements to shorten the goods transferring route and fully make use of the cooling energy of low temperature, gas being high in cost per unit heat.
That is, in cooling obtained by contacting goods with low temperature gas, convection heat transmission is most effective, and in convection heat transmission, cooling of goods by means of low temperature gas is affected by the heat transfer rate and the contacting time interval when the temperature difference between both is constant. The heat transfer rate is affected by the relatice speed of goods and low temperature gas, and the greater the relative speed is, the larger the heat transfer rate is, and also the longer the contact time interval is, the larger the heat transferred is.
Accordingly, to increase the heat transferred between goods and low temperature gas, when the relative speed between the goods and the low temperature gas is to be increased while the time interval of contact between the goods and the low temperature gas is to lengthened, the length of the goods transferring route must increase and consequently the size of the apparatus and construction cost is increased. On the other hand, as the goods transferring route is reduced, the efficiency of untilzing the cooling energy of low temperature gas is decreased, the cooling energy, being high in cost per unit, heat is not efficiently consumed.
The present invention, taking in consideration the problems above mentioned, has carried out the improvement of the method and apparatus for cooling.